Explosive-resin mixture for nonmetallic detonator



Feb. 18, 1964 A. M. ANZALONE 3,121,394

EXPLOSIVE-RESIN MIXTURE FOR NON-METALLIC DETONATOR Filed June 21, 1960 IN V EN TOR.

Jj. Wan 0.4%,. 9 M 24M United States Patent 3,121,394 EXPLUSIVE-RESIN MIXTURE FOR NON- METALLIC DETONATOR Alfred M. Anzalone, Succasunna, N1, assignor to the United States of America as represented by the Secretary of the Army Filed lane 21, 1360, Ser. No. 37,813 Claims. (Cl. 102-865). (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured for governmental purposes without the payment to me of any royalty thereon.

This invention relates to a new and improved detonator, particularly useful in mines.

Metallic detonators of the prior art have several disadvantages which this invention has overcome. First, the metal casing of prior detonators and the explosive compounds of the explosive train are frequently incompatible and measures must be taken to overcome this disadvantage such as by coating one or more components of the detonator with a lacquer. However, this is time consuming and often ineffective. Secondly, it is difficult and expensive to obtain a good waterproof and moisture proof seal at the end of the casing that is effective under extreme conditions of temperature and humidity commonly encountered. Third, the metals most commonly utilized, such as aluminum, copper and the like, are expensive and during War times shortages of these substances are unavoidable.

Further, while metallic detonators comprise a comparatively small component of a mine, usually about one inch in length and a quarter inch in diameter, they may provide the occasion for possible detection of nonmetallic mines in which they are used, and with modern mine detection equipment this possibility is greatly increased.

A primary object of this invention is to provide a detonator assembly free of metal parts.

Another object of the invention is to obtain a detonator having a primer charge that has sufficient sensitivity to stab action and yet has lost most of its sensitivity to impact and friction.

Still another object of the present invention is to obtain a nonmetallic detonato-r that is waterproof and moisture proof.

A further object of the invention is to provide a detonator assembly in which the problem of compatibility and adherence between the explosive and casing is eliminated.

These and other objects of the invention will be better understood by referring to the accompanying drawing in which:

FIGURE 1 is a longitudinal section View of the detonator in which a'cellulose cup is used as a casing; and

FIGURE 2 is a cross section taken on line 2-2 of FIGURE 1.

FIGURE 1 shows a cup casing 1 of uniform thickness which can be fabricated in a mold from a cellulose derivative according to known procedures. Within casing 1 is an explosive train composed of a base charge 2, an intermediate charge 3 and a primer charge 4.

The cellulose derivative which constitutes the cup casing may be a cellulose ether, such as ethyl cellulose, a cellulose ester, such as cellulose acetate or cellulose butyrate. The cellulose derivative to select for the casing depends on the desired tensile strength, compatibility with the explosive and exothermal heat characteristics. The confinement afforded with these cellulose cups is sufficient for high order detonation, it being well known that a defimite relationship exists between confinement and high order detonation.

3,121,394 Patented Feb. 18, 1964 The base charge may be cyclotrimethylenetrinitramine cyclotetramethylenetetranitrarnine, pentaerythrite tetranitrate, nitrocellulose, tetryl and other explosives.

The intermediate charge may be lead azide, dextrinized lead azide, mercury fulminate, diazodinitrophenol and others.

The sensitive stab-initiated primer charge is composed of a combination of a primary explosive mixture and a polyester resin. The primary explosive mixture is a detonating agent and consists of an oxidizing agent, such as potassium chlorate or barium nitrate and a fuel. The fuels used may be lead vthiocyanate, carbon black or antimony sulfide. The polyester resin utilized is any unsaturated type polyester which cures to a rigid polymer. A rigid unsaturated polyester may be defined as a product formed from the linear or straight chain condensation of any unsaturated dibasic acid such as maleic or fumaric and a glycol of ethylene, propylene, butylene and dipropylene. The resulting unsaturated resin is then blended with a reactive monomer such as vinyl acetate, methyl methacrylate or styrene. With the influence of heat and/or a peroxide catalyst, the mixture copolymerizes with the monomer, cross-linking the polyester molecules to produce a thermosetting solid. Typical among which are those sold under the trademark Paraplex. By virtue of the polyester resin, wholly contrary to expectation, the sensitive priming mixture when confined with said nonexplosive polyester resin still retains sensitivity to stab action and yet loses most of its sensitivity to impact and friction. Furthermore, a waterproof seal between the primer charge and the detonator casing is obtained because of the presence of the polyester resin.

The following examples are presented to show specific embodiments of the invention.

Example I A molded cellulose acetate cup casing similar to that shown in the drawing was prepared. Into this casing was loaded a base charge of cyclotrimethylenetrinitramine and then an intermediate charge of lead azide, both at predetermined loading pressures of approximately 10,000 p.s.i. The explosive-resin primer mixture was applied to the open end of the casing. The complete detonator was placed in an oven and cured at about 75 C. for about 15 minutes. The primer is composed of 8 parts, by weight, of lead thiocyanate-potassiurn chlorate (45/ mixture blended with 2 parts of the polyester resin. In this example about 0.4 gram of polyester resin was used for 2.2 grams of explosive. An amount of catalyst was previously added to the resin to cause the resin to cure in about 15 mintues at to C., and yet remain workable at room temperature for at least the necessary loading time. About one drop of catalyst was found ade' quate for this purpose.

The polyester resin was prepared by the Well known method of reacting maleic acid with propylene glycol. The polyester was then blended with about 0.1 gram of styrene and under the influence of heat, and about a drop of the catalyst ethyl methyl ketone peroxide suspended in dimethyl phthalate, a thermoset polyester resin was formed.

Example II The same procedure was followed in this example as in Example I except that 0.6 gram of the resin having the trademark Paraplex was used together with 2.4 grams of a mixture of lead thiocyanate-potassium chlorate (45/55) for the primer charge.

The primer charge therefore may consist of any unsatu' rated polyester resin, and its necessary diluents and catalysts, which cures to a thermoset or rigid polymer may be used, in combination with a fuel and oxidizing agent.

3 The unsaturated polyester resins are well known commer: cial products available under various trade-names such as Laminac produced by American Cyanamid, Paraplex produced by Rohm and Haas Co., Vibrin produced by Naugatuck Chemical Co. and others.

A great advantage of this invention lies in the safety with which the detonator casing may be loaded. The greater safety is predicated on the fact that the uncured resin explosive mixture is considerably less sensitive than the cured mixture, or other materials used as primers prior to this invention. In addition, in contrast to present practice, the usual procedure of loading is reversed so that the less sensitive base charge is loaded first and the more sen sitive priming charge is loaded last.

I claim:

,1. A detonator assembly comprising in combination an ethyl cellulose cup, a base charge of cyclotrimethylenetrinitramine and an intermediate charge of pressed lead azide in said cup, a stab-initiated primer charge at the open end of said cup, said primer charge comprising lead thiocyanate and potassium chlorate mixed with a thermoset polyester resin formed from the straight chain condensation of an unsaturated dibasic acid selected from the group consisting of maleic and furnaric acids, and glycol selected from the group consisting of ethylene, pro pylene, butylene and dipropylene glycol.

2. A detonator assembly as set forth in claim 1, wherein the resulting unsaturated resin is blended with a reactive monomer selected from the group consisting of vinyl acetate, methyl methacrylate and styrene.

3. A detonator assembly having improved safety comprising in combination a casing of a cellulose derivative elected from the group consisting of ethyl cellulose, cellulose acetate, and cellulose butyrate, a pressed base charge and intermediate charge in said casing, a sensitive stab-initiated primer charge adjacent said intermediate charge and sealing the open end of said casing, said primer charge composed of a fuel and an oxidizing agent mixed with a thermoset polyester resin formed from the straight chain condensation of an unsaturated dibasic acid selected it from the group consisting of maleic and fumaric acids, and a glycol selected from the group consisting of ethylene, propylene, butylene, and dipropylene.

4. A method of improved safety for loading detonators comprising pressing a base charge and an intermediate charge into a cup of a cellulose derivative selected from the group consisting of ethyl cellulose, cellulose acetate, and cellulose butyrate, and mixing an explosive-resin primer charge comprising an oxidizer, a fuel, and an unsaturated polyester resin with a reactive monomer, adding a peroxide catalyst to the explosive-resin charge to give a safe uncured explosive-resin, loading the primer charge into the open end of said cup, and heating at slightly elevated temperatures to cure said resin.

5 A method of improved safety for loading detonators comprising pressing a base charge and an intermediate charge into a cup of a cellulose derivative selected from the group consisting of ethyl cellulose, cellulose acetate, and cellulose butyrate, mixing an explosive-resin primer charge comprising a fuel, an oxidizer, and the condensation product of a reaction between maleic acid and propylene glycol, with styrene, adding a peroxide catalyst to the explosive-resin charge to give a safe uncured explosive resin, loading the primer into the open end of said cup, and heating at slightly elevated temperatures to cure said resin and make a stab-sensitive, waterproof detonator.

References (Iited in the file of this patent UNITED STATES PATENTS 1,437,224 Burns Nov. 28, 1922 1,984,846 Spaeth Dec. 18, 1934 2,410,801 Audrieth Nov. 12, 1946 2,767,655 Seavey Oct. 23, 1956 2,968,985 Seavy t Jan. 24, 1961 OTHER REFERENCES Rocket Propellants (Warren), published by Reinhold Publishing Corp. (New York) (1958). (Pp. 37 and 38 relied on.) 

3. A DETONATOR ASSEMBLY HAVING IMPROVED SAFETY COMPRISING IN COMBINATION A CASING OF A CELLULOSE DERIVATIVE SELECTED FROM THE GROUP CONSISTING OF ETHYL CELLULOSE, CELLULOSE ACETATE, AND CELLULOSE BUTYRATE, A PRESSED BASE CHARGE AND INTERMEDIATE CHARGE IN SAID CASING, A SENSITIVE STAB-INITIATED PRIMER CHARGE ADJACENT SAID INTERMEDIATE CHARGE AND SEALING THE OPEN END OF SAID CASING, SAID PRIMER CHARGE COMPOSED OF A FUEL AND AN OXIDIZING AGENT MIXED WITH A THERMOSET POLYESTER RESIN FORMED FROM THE STRAIGHT CHAIN CONDENSATION OF AN UNSATURATED DIBRASIC ACID SELECTED FROM THE GROUP CONSISTING OF MALEIC AND FUMARIC ACIDS, AND A GLYCOL SELECTED FROM THE GROUP CONSISTING OF ETHYLENE, PROPYLENE, BUTYLENE, AND DIPROPYLENE. 